fn main() {
    //只在栈上的数据：拷贝
    let x = 1;
    let y = x;
    println!("x = {}",x);
    println!("y = {}",y);

    let str = String::from("hello");
    let hi = str;
    //此处str报错，因为str为字符串，let hi = str;将str移动到hi中。
    //println!("say: {}",str);
    println!("say: {}",hi);


}
